A novel silk nanofiber composite membrane introduced from a self-porous polymer and a preparation method and application thereof

Abstract

The present application belongs to the field of organic solvent nanofiltration membrane, and particularly relates to a novel silk nanofiber composite membrane for introducing a crystalline self-porous polymer COF-TAPT-BTA into silk nanofiber SNF and used for organic separation and recovery, a preparation method and application thereof. The silk nanofiber has three-dimensional stereoscopic pores and flexible structure, which ensures the porosity and pore connectivity of the selection layer. The introduction of the COF can also provide additional, fast solvent molecule transfer microchannels, improve the permeation rate of solvent molecules, and realize the synchronous improvement of flux and solute selectivity.

Description

Technical Field

[0001] This invention belongs to the field of organic solvent nanofiltration membranes, and specifically relates to a novel silk nanofiber composite membrane that incorporates the crystalline self-porous polymer COF-TAPT-BTA into silk nanofibers (SNF) for organic separation and recovery, as well as its preparation method and application. Background Technology

[0002] Since the late 1960s, membrane separation technology has achieved remarkable results in water treatment, most notably in the successful application of reverse osmosis membranes in seawater desalination. In contrast, molecular separation technology based on organic solvent nanofiltration (OSN) is still in its nascent stage, with its first commercial success occurring in the early 1990s. Unlike nanofiltration systems that rely on size sieving and electrostatic interactions in water systems, OSN primarily relies on membrane pore size sieving. Nevertheless, achieving precise and rapid molecular separation using OSN membranes remains challenging in certain specialized fields, such as the separation and purification of components at the molecular scale in pharmaceutical manufacturing. Therefore, the design and fabrication of novel OSN membranes remains of great significance.

[0003] Polymers remain the primary material for preparing high-performance organic solvent separation membranes due to their ease of manufacture and scalability. However, the dense packing of linear segments in polymer materials limits the improvement of solvent flux. Furthermore, other membrane materials often involve the use of large amounts of organic chemicals in their synthesis or production processes; therefore, it is necessary to adopt simple, clean, and rapid processes to prepare stable and efficient OSN membranes. Summary of the Invention

[0004] The purpose of this invention is to provide a novel silk nanofiber composite membrane. The composite membrane uses a crystalline self-porous polymer COF-TAPT-BTA to construct a rapid transport channel, which can control the membrane morphology and can be used to accurately achieve organic solvent separation or solute / solute separation.

[0005] A novel silk nanofiber composite membrane incorporating a self-porous polymer is disclosed, wherein the separation layer of the membrane is obtained by combining the self-porous polymer COF with silk nanofiber SNF.

[0006] Furthermore, the self-porous polymer COF is COF-TAPT-BTA.

[0007] The structural formula of COF-TAPT-BTA is shown below:

[0008]

[0009] The COF-TAPT-BTA is prepared by an aqueous-phase induction method using the reactant monomers (4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine (TAPT) and 1,3,5-tricarboxyphenyl (BTA) via an amphiphilic L-valine derivative. It exhibits high crystallinity and a high specific surface area. The synthesis process is rapid and environmentally friendly, requiring only ten minutes of reaction in an aqueous solution.

[0010] In this invention, the preferred amphiphilic L-valine derivative is palmitoyl-L-valine, with the following structural formula:

[0011]

[0012] The reaction formula for preparing COF-TAPT-BTA is as follows:

[0013]

[0014] The preparation of COF-TAPT-BTA is an existing technology, as described in Nature Chemistry, 2023, 15, 841–847. The preparation can be carried out by referring to the above literature.

[0015] The silk nanofibers are obtained by peeling silkworm cocoons.

[0016] Specifically, silkworm cocoons were degummed, peeled, dialyzed, and centrifuged to obtain an aqueous dispersion of silk nanofibers.

[0017] The SNF dispersion of this invention is simple to prepare, and can be obtained by peeling and dialysis using a simple CaCl2-C2H5OH-H2O system. For example, the corresponding method is described in Chemical Engineering Journal, 2021, 415, 129021.

[0018] Furthermore, the loading of COF-TAPT-BTA on the base film surface was 0.00796 mg / cm³. 2 ~0.0215mg / cm 2 The loading of SNF on the membrane surface was 0.00796 mg / cm³. 2 ~0.0215mg / cm 2 .

[0019] In the preparation process, a dispersion of COF and a dispersion of SNF are mixed, and then the composite membrane is obtained by vacuum-assisted self-assembly on a base membrane. In the mixed dispersion, the mass ratio of SNF to COF-TAPT-BTA is 1 to 5:1.

[0020] Specifically, when preparing the membrane and measuring the dispersion, the loading content of SNF can be determined according to the membrane area (0.2 mg in this invention) to measure the SNF dispersion, and then the COF-TAPT-BTA dispersion can be measured according to the mass ratio.

[0021] After thoroughly mixing the measured SNF dispersion with the COF-TATPT-BTA dispersion, dilute to 200-300 mL and then sonicate for 1-3 minutes before further film preparation.

[0022] The mixed dispersion was deposited on the base film using a vacuum-assisted self-assembly method and then dried at 70–80 °C for 5 min.

[0023] The base film of the composite membrane is preferably a nylon base film. More preferably, a nylon base film with a pore size of 200 nm is used.

[0024] Silk nanofibers, belonging to the category of bio-based polymer nanofibers, offer a novel approach to solving key challenges in membrane separation technology due to their unique advantages such as simple preparation, high porosity, excellent flexibility, large specific surface area, and interconnected pore structure. These silk nanofibers can be obtained simply by exfoliation, achieving environmentally friendly and efficient preparation. Furthermore, as nanoscale components of silk, silk nanofibers (SNFs) possess stable peptide bond structures formed by amino acid condensation, exhibiting excellent resistance to organic solvents. Their high flexibility and self-assembly properties further broaden their application prospects in membranes.

[0025] This invention prepares a composite membrane on a nylon-based membrane by mixing a COF (COF-TAPT-BTA) dispersion and a silk nanofiber (SNF) dispersion and using a vacuum-assisted self-assembly method. The crystalline, self-porous polymer COF (covalent organic framework material) is used to construct solvent transport channels, while SNF provides a stable network framework. Simultaneously, its flexible structure fills the gaps between SNF and COF. COF-TAPT-BTA is used to construct ordered channels to facilitate rapid transport of solvent molecules.

[0026] The silk nanofiber composite membrane has excellent applications in the separation of organic solvents.

[0027] The composite membrane of this invention performs well in both solvent / solvent and solvent / solute separation processes, directly using two dye molecules, Red 23 and Reactive Black 5, as reference molecules and simulating solutes in organic solvents.

[0028] The SNF / COF nanocomposite membrane of this invention exhibits excellent solvent permeability (1365.51 L·m⁻¹ for methanol). -2 ·h -1 ·bar -1The ethanol content was 669.52 L·m³. -2 ·h -1 ·bar -1 The membrane exhibits a rejection rate of over 95% for Direct Red 23 (DR 23) and Reactive Black 5 (RB 5). Furthermore, solute separation tests using the composite membrane of this invention demonstrate excellent separation performance for mixed solutes of different molecular sizes. Simultaneously, the SNF / COF membrane preparation method provided by this invention is environmentally friendly, low-cost, simple to operate, and easy to mass-produce.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention utilizes a vacuum-assisted self-assembly method to rapidly prepare a composite membrane on the surface of a base film by mixing SNF dispersion and COF-TAPT-BTA dispersion, without involving chemical reactions, thus greatly improving environmental friendliness. Silk nanofibers possess three-dimensional pores and a flexible structure, ensuring the porosity and channel connectivity of the selective layer. Furthermore, the introduction of COF provides additional, rapid microchannels for solvent molecule transport, increasing the permeation rate of solvent molecules and achieving a simultaneous improvement in flux and solute selectivity. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the preparation of silk nanofibers (SNF) in this invention.

[0032] Figure 2 This is a schematic diagram illustrating the preparation of the SNF / COF composite membrane in this invention;

[0033] Figure 3 These are SEM images of the surface and cross-section of the optimal membrane in this invention (i.e., Example 3). Detailed Implementation

[0034] The technical solution of the present invention is illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0035] The preparation method of the SNF dispersion used in the following examples is as follows:

[0036] Prepare 1000 mL of Na₂CO₃ aqueous solution (0.5 wt%). Cut silkworm cocoons (with pupae removed) into strips, weigh 10 g, and place them in 500 mL of boiling Na₂CO₃ solution. Boil for 30 minutes, then discard the liquid. Add the remaining 500 mL of Na₂CO₃ solution and boil again for 30 minutes. This step promotes the separation of sericin from silk fibers, thereby obtaining silk microfibers.

[0037] The degummed silk microfibers were rinsed with a large amount of deionized water. The dried fibers were collected by natural drying and then thoroughly mixed with CaCl2, anhydrous ethanol and deionized water (molar ratio of 1:2:8, total volume controlled at 300 mL). The mixture was stirred continuously at 60 °C until the fibers were completely dissolved.

[0038] The solution was then subjected to thorough dialysis for two days (dialysis membrane specifications: MWCO = 14000 Da), with the deionized water changed 3-4 times daily. After dialysis, the dialysate was carefully collected and centrifuged at 9000 rpm for 20 minutes to effectively remove impurities and precipitates. The centrifuged liquid was collected, and the concentration of the SNF solution was accurately determined using a sampling and drying method. The final solution was diluted to obtain an SNF dispersion of 0.225 mg / mL.

[0039] Example 1

[0040] A novel composite membrane (i.e., a novel silk nanofiber composite membrane) is prepared by introducing a crystalline, self-porous polymer COF into silk nanofibers for organic solvent separation. The preparation method includes the following steps:

[0041] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0042] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes (500 rpm). Then, sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL).

[0043] 3) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), and then measure 10 mL of COF-TAPT-BTA dispersion at a mass ratio of 1:1 with the SNF dispersion and mix them together. Dilute the mixture to 200 mL, sonicate again for 1 minute, and filter the mixture through a vacuum (0.098 MPa) onto the surface of a nylon-based membrane to prepare an SNF / COF-1 composite membrane;

[0044] 4) Dry the obtained SNF / COF-1 composite membrane at 80℃ for 5 minutes and store it for testing.

[0045] In this embodiment, ultrasound can be performed at a power of 336W, but this power has no effect on the experimental results, and the same applies below.

[0046] Example 2

[0047] A composite membrane for organic solvent separation by introducing a crystalline, self-porous polymer COF into silk nanofibers is prepared by the following steps:

[0048] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0049] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes (500 rpm, the same below). Then, sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL).

[0050] 3) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), and then measure 5 mL of COF-TAPT-BTA dispersion and mix it with the SNF dispersion at a mass ratio of 2:1. Dilute the mixture to 200 mL, sonicate again for 1 minute, and filter the mixture through a vacuum filter onto the surface of a nylon-based membrane to prepare an SNF / COF-2 composite membrane;

[0051] 4) Dry the obtained SNF / COF-2 composite membrane at 80℃ for 5 minutes and store it for testing.

[0052] Example 3

[0053] A composite membrane for organic solvent separation by introducing a crystalline, self-porous polymer COF into silk nanofibers is prepared by the following steps:

[0054] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0055] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes, then sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL);

[0056] 3) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), and then measure 3.33 mL of COF-TAPT-BTA dispersion according to a mass ratio of 3:1 to SNF dispersion, and mix them together. Dilute the mixture to 200 mL, sonicate again for 1 minute, and filter the mixture through a vacuum filter onto the surface of a nylon-based membrane to prepare an SNF / COF-3 composite membrane;

[0057] 4) Dry the obtained SNF / COF-3 composite membrane at 80℃ for 5 minutes and store it for testing.

[0058] Example 4

[0059] A composite membrane for organic solvent separation by introducing a crystalline, self-porous polymer COF into silk nanofibers is prepared by the following steps:

[0060] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0061] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes, then sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL);

[0062] 3) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), and then measure 2.5 mL of COF-TAPT-BTA dispersion according to a mass ratio of 4:1 with the SNF dispersion. Dilute the mixture to 200 mL, sonicate again for 1 minute, and filter the mixture through a vacuum filter onto the surface of a nylon-based membrane to prepare an SNF / COF-4 composite membrane;

[0063] 4) Dry the obtained SNF / COF-4 composite membrane at 80℃ for 5 minutes and store it for testing.

[0064] Example 5

[0065] A composite membrane for organic solvent separation by introducing a crystalline, self-porous polymer COF into silk nanofibers is prepared by the following steps:

[0066] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0067] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes. Then, sonicate in a 336 W ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL).

[0068] 3) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), and then measure 2 mL of COF-TAPT-BTA dispersion according to a mass ratio of 5:1 with SNF dispersion. Mix the mixture with the SNF dispersion. Dilute the mixture to 200 mL, sonicate again for 1 minute, and filter the mixture through a vacuum filter onto the surface of a nylon-based membrane to prepare an SNF / COF-5 composite membrane.

[0069] 4) Dry the obtained SNF / COF-5 composite membrane at 70℃ for 5 minutes and store it for testing.

[0070] Comparative Example 1

[0071] A composite membrane for organic solvent separation, wherein the membrane is prepared by means of the following steps:

[0072] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0073] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes, then sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL);

[0074] 3) Take 5 mL of COF-TAPT-BTA dispersion, dilute it to 200 mL, sonicate it again for 1 minute, and filter it through a vacuum filter onto the surface of a nylon-based membrane to prepare a COF-0.1 composite membrane;

[0075] 4) Dry the obtained COF-0.1 composite membrane at 70℃ for 5 minutes and store it for testing.

[0076] Comparative Example 2

[0077] A composite membrane for organic solvent separation, wherein the membrane is prepared by means of the following steps:

[0078] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0079] 2) Add 2 mg of synthesized COF-TAPT-BTA to 100 mL of deionized water and stir magnetically for 30 minutes. Then, sonicate in an ultrasonic water bath for 30 minutes to obtain COF-TAPT-BTA dispersion (0.02 mg / mL).

[0080] 3) Measure 13.5 mL of COF-TAPT-BTA dispersion, dilute it to 200 mL, sonicate it again for 1 minute, and filter it through a vacuum to the surface of the nylon base membrane to prepare a COF-0.27 composite membrane.

[0081] 4) Dry the obtained COF-0.27 composite membrane at 70℃ for 5 minutes and store it for testing.

[0082] Comparative Example 3

[0083] A composite membrane for organic solvent separation by loading silk nanofibers (SNF) alone is prepared by the following steps:

[0084] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0085] 2) Measure 0.445 mL of SNF dispersion (containing 0.1 mg SNF), dilute the liquid to 200 mL, sonicate again for 1 minute, and filter it through vacuum to the surface of the nylon base membrane to prepare an SNF-0.1 composite membrane;

[0086] 3) Dry the obtained SNF-0.1 composite membrane at 70℃ for 5 minutes and store it for testing.

[0087] Comparative Example 4

[0088] A composite membrane for organic solvent separation by loading silk nanofibers (SNF) alone is prepared by the following steps:

[0089] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0090] 2) Measure 0.889 mL of SNF dispersion (containing 0.2 mg SNF), dilute the liquid to 200 mL, sonicate again for 1 minute, and filter it through vacuum to the surface of the nylon base membrane to prepare an SNF-0.2 composite membrane;

[0091] 3) Dry the obtained SNF-0.2 composite membrane at 70℃ for 5 minutes and store it for testing.

[0092] Comparative Example 5

[0093] A composite membrane for organic solvent separation by loading silk nanofibers (SNF) alone is prepared by the following steps:

[0094] 1) Soak the nylon base membrane in ultrapure water one day in advance and ultrasonically treat it in a water bath for 30 minutes to thoroughly remove dust;

[0095] 2) Measure 1.2 mL of SNF dispersion (containing 0.27 mg SNF), dilute the liquid to 200 mL, sonicate again for 1 minute, and filter it through vacuum to the surface of the nylon base membrane to prepare an SNF-0.27 composite membrane;

[0096] 3) Dry the obtained SNF-0.27 composite membrane at 70℃ for 5 minutes and store it for testing.

[0097] The methanol flux and dye rejection rate in organic solvents of the SNF / COF, SNF, and COF composite membranes prepared in the test examples and comparative examples were tested at room temperature under a stainless steel dead-end filtration device at a pressure of 0.2 MPa.

[0098] Table 1 shows the methanol solvent flux of the composite membranes prepared in Example 3 and Comparative Examples 1-5, as well as the dye rejection rates of the relevant organic solvent nanofiltration membranes reported in the literature. The data errors are all within a reasonable error range.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from the table, the performance of the COF-0.1 and COF-0.27 membranes in the comparative examples is only slightly better than that of the nylon-supported membrane. This indicates that the membrane formed by COF alone cannot be continuously spread on the surface of the nylon-based membrane. This may be due to the strong interaction between the COF-TAPT-BTA materials, which tend to agglomerate when formed individually. Unlike the COF composite membrane, when the amount of SNF increases from 0.1 mg to 0.2 mg, the methanol permeation coefficient of the SNF membrane in the comparative examples decreases from 3736.55 to 679.10 L·m. -2 ·h -1 ·bar -1 The DR 23 rejection rate also increased to 96.27%. Further increasing the SNF amount to 0.27 mg resulted in a DR 23 rejection rate of 99.46% for the SNF-0.27 membrane pair, while the methanol permeability decreased to 411.11 L·m³. -2 ·h -1 ·bar -1 This indicates that a continuous SNF separation layer was successfully formed.

[0103] It is worth noting that, as in the embodiments, when the ratio of SNF to COF is fixed at 3:1, the membrane not only maintains the high retention performance of the SNF membrane for DR 23 and RB 5, but also achieves a methanol permeability of 1365.51 L·m -2 ·h -1 ·bar -1 (Twice that of the original SNF-0.2 membrane). Compared with some previously reported membranes such as TFP-DHF membranes, NPTs-rGO membranes, and (PpPD-TMC) / HPAN membranes, the SNF / COF-3 membrane also exhibits a higher methanol permeation coefficient and rejection rate. This indicates that COF-TAPT-BTA can act as a "channel" to provide an additional pathway for solvent molecules to permeate through the membrane, thereby increasing the solvent molecule permeation coefficient, and that defect-free SNF / COF composite membranes can be constructed.

[0104] Table 2 shows the methanol permeation coefficient and dye molecule rejection rate of the SNF / COF composite membranes prepared in Examples 1-5. The data errors are all within a reasonable error range.

[0105] Table 2

[0106]

[0107] As shown in the table, the amount of SNF in the examples was fixed at 0.2 mg. The amount of COF-TAPT-BTA was varied, and the pure solvent permeation coefficient and the rejection rates of DR 23 and RB 5 for different membranes were tested. When the ratio of SNF to COF-TAPT-BTA was 1:1 and 2:1, the methanol permeation coefficient of the SNF membrane was greater than 1500 L·m⁻¹. -2 ·h -1 ·bar -1 The rejection rates for DR 23 were 87.35% and 93.24%, respectively, and the rejection rates for RB 5 were 74.28% and 87.45%, respectively. This is because the high loading of COF-TAPT-BTA itself affects the integrity of the SNF layer to some extent. Furthermore, when the SNF / COF ratio is low, COF accumulates on the membrane surface, hindering the full utilization of the channels. Notably, when the SNF / COF ratio further changes to 3:1 (i.e., the COF proportion decreases to 1 / 3), the membrane not only maintains high rejection performance for DR 23 and RB 5, but also achieves a methanol permeability of 1365.51 L·m³. -2 ·h -1 ·bar -1 It is speculated that at this point, COF-TAPT-BTA is more uniformly dispersed on the membrane surface and does not significantly cause defects on the membrane surface. Simultaneously, COF-TAPT-BTA is tightly encapsulated by SNF, thus forming a heterogeneous structure within the SNF / COF membrane that can function as a channel. Figure 3 It can be observed that COF-TAPT-BTA is more uniformly dispersed on the membrane surface at this time, and does not cause significant defects on the membrane surface. At the same time, COF-TAPT-BTA is tightly wrapped by SNF, and COF, as a solvent molecule transport channel, passes through both sides of the SNF membrane, thus forming a heterostructure that can serve as a channel in the SNF / COF membrane.

[0108] When the SNF / COF ratio continued to change to 4:1, although the methanol permeability remained high at 1075.24 L·m -2 ·h -1 ·bar -1 However, the retention rates of DR 23 and RB 5 no longer increased significantly at this point. When the SNF / COF mass ratio was further changed to 5:1, the methanol permeability decreased to 773.21 L·m³. -2 ·h -1 ·bar -1The rejection rates for DR 23 and RB 5 no longer increased. It can be inferred that due to the reduced loading of COF-TAPT-BTA at this point, the number of channels available for additional solvent transport on the membrane also decreased, thus reducing the transport rate of solvent molecules. However, the relatively dense SNF network still ensured a high rejection rate. The SNF / COF-3 membrane in Example 3 showed the most outstanding performance, with a methanol permeability of 1365.51 L·m⁻¹. -2 h -1 ·bar -1 DR 23 rejection rate: 96.08%; RB 5 rejection rate: 95.95%. It is evident that by using an appropriate SNF / COF ratio in membrane preparation, COF can act as a "channel" to provide an additional pathway for solvent molecules to permeate through the membrane, thereby increasing the solvent molecule permeation coefficient, and SNF / COF composite membranes can be constructed.

[0109] In addition, the solute / solute separation performance of the optimal embodiment SNF / COF-3 membrane was tested at room temperature and 1 bar pressure.

[0110] Table 3

[0111]

[0112] As shown in the table, after separation of the mixed solution, smaller molecules such as MO (methyl orange), MLB (methylene blue), and CV (crystal violet) permeated and were predominantly present in the permeate. In contrast, larger molecules such as CR (Congo red), DR 23 (direct red 23), and RB 5 (active black 5) were successfully retained in the permeate. This demonstrates that SNF / COF membranes have certain application potential for separating solute molecules of two different sizes.

Claims

1. A method for preparing a silk nanofiber composite membrane incorporating a self-porous polymer, characterized in that, The separation layer of the membrane is obtained by combining a self-porous polymer COF with silk nanofiber SNF. The self-porous polymer COF, using COF-TAPT-BTA, is prepared from the reactive monomers 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 1,3,5-tricarboxyphenyl. The composite membrane is obtained by blending a COF dispersion with a SNF dispersion and then stacking them on a base membrane using a vacuum-assisted self-assembly method. The mass ratio of SNF to COF-TAPT-BTA in the mixed dispersion is 1~5:

1.

2. The method for preparing the silk nanofiber composite membrane as described in claim 1, characterized in that, The loading amounts of COF-TAPT-BTA and SNF on the base film surface were both 0.00796 mg / cm³. 2 ~0.0215 mg / cm 2 .

3. The method for preparing the silk nanofiber composite membrane as described in claim 1, characterized in that, The mixed dispersion was deposited on the base film using a vacuum-assisted self-assembly method and then dried at 70-80℃ for 5 min.

4. The method for preparing the silk nanofiber composite membrane as described in claim 1, characterized in that, The COF-TAPT-BTA is prepared by aqueous-phase induction using the reaction monomers 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 1,3,5-tricarboxymethylbenzene via an amphiphilic L-valine derivative.

5. The method for preparing the silk nanofiber composite membrane as described in claim 1, characterized in that, The silk nanofibers are obtained by peeling silkworm cocoons.

6. The method for preparing the silk nanofiber composite membrane according to any one of claims 1-5, characterized in that, The base film of the composite membrane is a nylon base film.

7. The silk nanofiber composite membrane with self-porous polymer introduced by any of the preparation methods of claims 1-6.

8. The application of the silk nanofiber composite membrane with self-porous polymer as described in claim 7 in the separation of organic solvents.

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